Method and apparatus for exhausting and filling discharge devices



May 26, 1942.

c. Bol.. .2,284,036

METHOD AND APPARATUS FOR EXHAUSTING AND FILLING DISCHARGE DEVICES Filed May l2, 1941 ',ff- :5g I: 5 i 29 f 'l -f.' f," ...J

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Cornelis Bol",

Inventor:

Patented May 26, 1942 METHOD AND APPARATUS FOR EXHAUST- ING AND FILLING DISCHARGE DEVICES Cornelis Bol, Palo Alto, Calif., assignor to General Electric Company, a corporation of New York Application May 12, 1941, Serial No. 393,004

13 Claims.

My invention relates to a method and apparatus for exhausting, filling and sealing discharge devices and more particularly to a method and apparatus for exhausting all contamination from said devices, for introducing gaseous and vaporizable materials into said devices and for sealing definite proportions of said material therein.

The exhaust phase of myinvention provides for the removal of the occluded gases and other contamination from the parts of the discharge device as well as the exhaustion of the interior thereof. The gas-tight connection established during the exhaust phase must function until the discharge device is filled and sealed.

The filling phase of my invention provides for the insertion of the proper amounts of gaseous and/or vaporizable materials constituting the discharge supporting components of the discharge device. The gaseous and vaporizable components establish, to a large degree, the operating characteristics of the discharge device and are provided in definite amounts in order to .develop definite pressures, etc., therein. In the filling operation great care must be exercised to prevent contamination from being carried into the discharge device with the gaseous and vaporizable materials.

Certain types of discharge devices, such as those generally referred to as capillary lamps, are made of quartz or hard glass and, being very difficult to Work to definite dimensions, normally vary somewhat from each other. These variations are usually very minute but must be taken into account when the lamps are filled or said lamps will differ greatly in their operating characteristics. Prior to my present invention, it was necessary to compensate for these variations after the lamp was sealed and tested since no method or apparatus was known which could introduce the correct amounts of these materials into the lamp in every instance. The method of compensation consisted in providing the exhaust tubulation adjacent one of the electrodes and in sealing off said tubulation a short distance from the envelope so that storage space was provided for an excess of the vaporizable material at said location. Tests were then conducted to determine the operating characteristics of the lamp whereupon an estimated compensation was made by reducing the size or length of the tubulation so as to force some of the vaporizable material condensed therein into the immediate interior portion of the lamp. A second test had to be made to determine the effect of the adjustment after which other adjustments and tests often had to be made to cause the lamp to operate as desired. The above method of manufacture, which is disclosed in detail in U. S. Patent No. 2,094,694. dated October 5, 1937, is somewhat objectionable since it is indirect and costly and since a considerable portion of the exhaust tubulation must remain on the lamp.

One object of my invention is to provide a method and apparatus of exhausting and lling discharge devices in a more satisfactory and ready manner than practiced heretofore. My' method allows the effective exhaustion of the device and the proper proportioning and ready introduction of uncontaminated filling materiais.

Another object of my invention is to provide a method and apparatus of exhausting and filling discharge devices which provides for the proportioning of the filling materials in relation to the construction of said discharge devices. The method and apparatus permits the operating characteristics of the discharge `device to be established before it is sealed and causes said devices to have definite operating characteristics when completely manufactured. The method and apparatus eliminates prior cumbersome methods of operation and the need for a tubulation ortip on the device. The tubulation interferes with the application of said devices and the flow of the cooling medium about the device.

Other objects and advantages of my invention will appear from the following detailed description of a method and apparatus comprising my invention which is used in the manufacture of capillary lamps.

In the drawing; Fig. 1 is a schematic illus-A tration of apparatus comprising my invention; Fig. 2 is a side elevation of manifold and control valves thereof from which a quarter section has been taken; and Fig. 3 is a section through means for forcing additional vaporizable material to the discharge device according to a, modification of my invention.

According to the preferred method of operation, the whole apparatus must be evacuated for a time before the exhaustion of a discharge lamp is attempted, so as to rid the apparatus of materials contaminating a discharge lamp. Thev exhaust operation is brought about when a closed tube is attached to the central opening l0 in the manifold Il in place of the capillary exhaust tube l2 of the discharge lamp I3 shownso that the apparatus is in effect a closed system sealed from further contamination. The closed tube in the opening Il) most generally is the portion of the exhaust tube l2 tipped oif from a discharge lamp I3 during the preceding cycle of operations and is sealed to the manifold Il by the pressure of the compression nut Il against the rubber gasket l5 (Fig. 2). The opening Ill extends into'the manifold Il but a short distance and connects with four transverse pastransverse passages are at 90 degree intervals and are for thel purpose of conducting fluids to and from similarly spaced passages or outlets on the back of the manifold Il, corresponding to the passage or outlet 2| (Fig. 2), as the control valves I'I, I8, I9 and .20 may demand. Each control valve is a duplicate of the others and consists of a stem 22 screwed into anopening in the manifold Il, a valving needle 23 screwed into the stem 22 and engaging a seat in said manifold I-I, packing 24 and packing nut 25. In this particular instance, the packing 2l is of leather which has been impregnated by anhydrous lanum and beeswax in vacuum.

At the time the exhaust cycle which clears the contamination from the apparatus is in effect, all four valves I1, I3, I9 and 20 are turned to their open positions and a source of vacuum connected to the manifold I I through pipe 26, outlet 2l and valve I1 is permitted to drawon the central opening I in said manifold I I closed by the tube and each of the auxiliary systems controlled by the valves I8, I9 and 20. If the apparatus is of heat to reservoir 23 so that the mercury separated from any less volatile material it may contain. The electric heater 31 provides `the means of heating reservoir 23 which retains the less volatile materials. 'I'he stopcock 3I is now turned so that an inert gas, preferably argon, is admitted into the auxiliary system from the connection 33 and the mercury in the reservoir 30 is forced up the tube `32 to the reservoir 33.

Stopcock 3| is then turned so that vacuum is again applied to the system whereupon stopcock 34 is turned so that aninert gas connection is made to the reservoir 33 from the pipe 3l. These operations transfer and are only successful in that tube 32 has `an upwardly extending loop therein, of 85 ycentimeters in height for instance, which holds a sufilcient column of mercury to block any movement thereof with the difference in pressures produced within the system.

In certain instances, it may be possible to introduce suiciently clean distilled mercury directly into the reservoir 33 to satisfy the requirel ments of the discharge device being treated, but

being placed in operation after an inactive period, it is preferred that the different parts thereof be heated to cause all possible contamination to be liberated and exhausted. The length of time the exhaust cycle is lcarriedon depends upon the prior usage of the complete system and is terminated, after the valves I8, I9 and 20- are closed, by closing valve I1.

The apparatus is not inf condition to start exhausting the discharge lamp until it is provided with a supply of the vaporizable material, the non-gaseous component of the lling. `The vaporizable material, which is mercury in this particular instance, readily absorbs the atmosphere and other materials which could contaminate a discharge lamp and considerable care must be exercised to prevent contamination from being carried into the discharge lamp with said material. The preferred method of operation consists in introducing the mercury into a particular auxiliary system of the apparatus in as clean and uncontaminated a state as possible, and to treat said mercury in said systeml so as to ,rid it of all possible contamination. The preferred method of introducing the mercury into the system consists in sucking the mercury into the apparatus through a second downwardly bent tube (not shown) inserted in the central opening IIl of the manifold II in place of the closed tube. The lower end of the bent tube is immersed in a dish of clean distilled mercury whereupon valve I3 is opened so that the auxiliary system including pipe 21, reservoir 2B, pipe 29, reservoir 3U and stopcock 3l are connectedto said tube. The remainder of the auxiliary system includes tube 32, reservoir 33, stopeock 34 and pipe 35 which are connected to valve I9 of the manifold II and is completely sealed as stopcock 34 and valve I9 are now at the closed position. The mercury is sucked up through the bent tube, the manifold I I and into the reservoir 28,by turning the stopcock 3| so that a source of vacuum connected thereto at 36 can draw on the auxiliary system. When the reservoir 28 is su'iciently filled, valve I8 and the stopcock 3| are closed. This method of `operation keeps the auxiliary system from being opened to the atmosphere while the mercury is introduced therein.

The next step in the method is to distill the mercury over into reservoir by the application even at such times it is preferred that the meroury be heated in reservoir 33 while under vacuum to remove certain undesirable contaminating elements which can be drawn ou with the exhaust. In such cases, the tube 32, reservoirs 28 and 33 and the remainder of the auxiliary system are not required.

In any case, the apparatus is now ready to exhaust and fill the the discharge deviceand accordlngly the exhaust capillary or tube I2 of the capillary discharge lamp I3 which is to be treated is connected to the central opening I0 in the manifold I I. When this has been done, the valve I1 is opened so that the lamp is drawn on by vacuum, and heat is applied to the lamp `I3 to drive out all gases contained within the lamp assembly. Although the lamp I3 is quartz, it is preferred that it be heated as hot as possible without danger of collapsing. When the lampv I3 is believed to be thoroughly exhausted, the valvev I1 is closed and the heating is stopped.

The filling operation is now brought about by opening valve 20 thereby admitting the gas conducted thereto through tube 4II and stopcock 4I. Two connections 42 and I3 are made to the stopcock Il so that a choice of two different gases, usuallyargon or neon or mixtures thereof, can be supplied the lamp I 3. A monometer M is also connected to thevtube I0 in order that the lamp I3 can be filled to a known pressure, said pressure in the ordinary instance being such that the internal pressure of the lamp after receiving its charge of mercury is equivalent .to a 2 om. co1- umn of mercury. l

To the filling inthe lamp I3 is nowadded a l vfilled varies somewhat from the predecessors.

Absolute control over the size of the interior of the lamp has, as yet, been impossible as the en closing envelope is either of quartz or yhard glass which is diflicult to work and as the interior is so small as to be materially affected by very slight variations in all parts of the lamp I3. According to my method of operation, the valve 20 is closed sealing off the gas filled portion of the mercury to reservoir 33 v the apparatus and the valve I9 is opened permitting the mercury to ow through the manifold and the capillary tube I2 to the lamp I3. The movement of the mercury, of course, forces the gas contained within the manifold II and the capillary tube I2 into the lamp I3 and is preferably controlled so that the gas is at a pressure equivalent to a 2 cm. column of mercury when the valve I9 is closed and the filling operation is terminated. An excess of mercury is then contained within the lamp I3 or is evaporated thereunto by heating the exhaust capillary I2 which is now filled with mercury and a very subnormal discharge started between the electrodes 45 and 46 of said lamp I3. The lamp I3 is then permitted to cool, whereupon the trough "41 containing cool water is' raised over it and the normal discharge is created in it. The lead 48 which is connected to one end of the lamp I3 is insulated to prevent a discharge of current through the water which is, in turn, circulated through the trough from the inlet 50 to the outlet 5I.

Since there is too much mercury within the lamp I3, it is now operating incorrectly and the voltage of the electrical energy across the terminals thereof, asindicated by the voltmeter 52, is above normal. The valve I9 is then turned back very slightly so that the pressure of the mercury -vapor within the lamp I3 which has now increased to several atmospheres pressure can escape into the exhaust capillary I2 by forcing the mercury within the exhaust capillary I2,to back away from said lamp I3. The electrical voltage across the electrodes 45 and 46 of the lamp I3 drops as the pressure drops and finally the lamp I3 is operating as desired and the valve I9 is closed. As such times, the mercury lls the entire exhaust capillary I2 and should be just at the verge of entering the lamp I3.

If the method of manufacture has been such that the lamp I3 contains less than the desired amount of mercury, the method of operation must be varied somewhat. In such instances, the additional mercury is introduced into the lamp I3'in either of twoways; one being by discontinuing the operation of the lamp I3 and forcing in more mercury from reservoir 33 by increasing the pressure of the gas introduced through stopcock 34, and the other being by mechanically forcing more mercury into the lamp I3 while it is still operating. In the latter instance, it is preferred that a plunger 53,-' like that shown in Fig. 3, be provided in the manifold II between valves I1 and I9 so that suflicient pressure can be supplied to the mercury to force it into the lamp I3 against the 200 to 300 atmospheres of pressure therein. The plunger 53 is sealed into the man1- fold I-I in the samey manner as the metering -needle 23 of the valves I1, I8, I9 and 20, and is operated by screwing it in or out of the stem 54.

The next operation is to disconnect the electrical circuit from the lamp I3 whereupon 1t cools and the mercury vapor in it condenses on the walls of the envelope reducing the pressure therein. The mercury in the exhaust capillary I2 does not move into the lamp I3 as it is incapable of expanding with the change in pressure within-said capillary I2, but must be drawn away from the lamp I3 a little distance before said capillary I2 can be sealed and tipped off. The mercury is drawn back in the exhaust capillary I2 by turning the stopcock 34 so that the vacuum connection 55 can draw on the mercury in the reservoir 33 and opening the valve I9 slightly for an interval. The drawingback of the mercury only causes a change in the amount of the gaseous component of the lling in the lamp I3 which change can be provided for in the original supply of said component introduced into said lamp I3, and is relatively unimportant with respect to the non-gaseous component of said filling. The exhaust capillary I2 is now tipped oil' as close to the lamp I3 as the Water in the bath will permit.

The method of operation develops a small tip at the middle of the lamp I3 which is much less objectionable than the longer tube and `tip developed at the end of the lamp I3 by prior methods of operation. 'I'he present tip can, however, be reduced in size still further so as to virtually be non-existent if desired. To shorten the' tip, the lamp I 3 must first be placed in a suitable bath, molten tin or lead, at a temperature such that it increases the pressure within the lamp I3 to about one atmosphere, whereupon the tip can be treated by a flame in any manner required. A lamp manufactured in this way is both stronger and better looking and oers less resistance to the ilow of the cooling-watery in 1. The method of exhausting and iilling a discharge device which comprises connecting the device to exhausting and lling apparatus, exhausting said device, introducing a vaporizable material into said device, creating adischarge therein, establishing the operating characteristics of vthe device by readjusting the amount of vaporizable material within the device and thereafter sealing said device from the exhausting and lling apparatus.

2. The method of exhausting and lling a discharge device which comprises connecting the device to exhausting and filling apparatus, exhausting said device, introducing an excess of a vaporizable material into said device, creating a discharge in said device, establishing the operating characteristics of the device by releasing the excess vaporizable material therefrom and thereafter sealing said device from the exhausting and filling apparatus.

3. The method of exhausting and filling a discharge device which comprises connecting the device to exhausting and filling apparatus, exhausting said device, introducing a vaporizable material into said device, creating a discharge therein so as to determine the operating characteristics of the device, discontinuing the operation of the device to cause the pressure therein to be reduced, introducing additional vaporizable material into said device, recreating a discharge in said device, establishing the operating characteristics of the device by releasing the excess vaporizable material therefrom and thereafter sealing said device from the exhausting and filling apparatus.

4. 'I'he method of exhausting and filling a discharge device which comprises connecting the device to exhausting and iilling apparatus, ex-

' vice, creating a discharge .terlal from the device to provide an excess thereof over hausting said device, introducing a ,vaporizable material into said device, creating a discharge therein, so as to determine the operating characteristics of the device, forcing additional vaporizable material into said device until definite operating characteristics are established by said device and thereafter sealing the said device from the exhausting and lling apparatus.

5. The method of exhausting and filling a dis- 6. The method of exhausting and filling a discharge device provided with an exhaust tube which comprises connecting the exhaust tube of the devicey to exhausting and filling apparatus,

exhausting said device, filling said. device '-to a definite pressure with a gaseous atmosphere, introducing a vaporizable material into said dein the device' to determine'the operating characteristics thereof, adjusting said characteristics to definite values either by adding or releasing vaporizable mathrough the tube and thereafter sealing and tipping off said tube adjacent the device 'to separate said device from the exhausting and filling apparatus.

'7. 'Ihe method of exhausting and lling a discharge device which oomprises'connecting the device to exhausting and filling apparatus, exhausting said device, heating the device externally to cause the liberation of any contamination so that it is drawn oil.' with the exhaust,

filling the device with a gaseous atmosphere, introducing a vaporizable material into said device, creating a discharge therein, establishing the operating characteristics of the device by readjusting the amount of vaporizable material within the device and thereafter sealing -said device from the exhausting and filling apparatus.

8. The method of exhausting and filling a discharge device lprovided with an exhaust tube which comprises connecting the exhaust tube of the device to exhausting and filling apparatus, exhausting said device, filling the device with a gaseous atmosphere, introducing a suihcient quantity of a vaporizable material into the tube the amount vaporized by a discharge in the device and to cause the gas within the device to be compressed to a definite pressure and a portion of said material to enter the device, creating a. dischargein the device to determine the operating characteristics thereof, establishing definite operating characteristics for the device by permitting the excess vapor therein to re-enter the tube, and thereafter sealing and tipping off the tube adjacent the device to separate the device from. the exhausting and filling apparatus. Y

9. Apparatus for exhausting and filling a discharge device provided with an exhaust tube comprising a manifold having a plurality of outlets adapted to be connected to sources of vacuum and the different lling materials, means for connecting the exhaust tube of the device to said manifold and needle valves connectedv to the outlets of the manifold for controlling the exhausting and filling operations.

10. Apparatus for exhausting and filling a' discharge device Vprovided with an exhaust.V tube comprising a manifold having a plurality of cutlets adapted to be connected to sources of vacuum and the different filling materials, means for connecting the exhaust tube of the device to said manifold, a reservoir connected to one of said outlets adapted to hold a vaporizable material, means connected to said reservoir for varying the pressure therein and the tendency of said vaporizable material to travel toward the manifold, and needlevalves connected to the outlets of the manifold for controlling the exhausting and filling operations. x

1l. Apparatus for exhausting and lling a discharge device provided with an exhaust tube comprising a manifold having a plurality of outlets adapted to be connected to sources of `vacuum and the different lling materials, means for connecting the exhaust tube of thedevice to said manifold, a reservoir connected to one of said outlets, a second reservoir connected to said rst reservoir adapted to hold a vaporizable material, heating means for said second reservoir yto distill the vaporizable material into the first reservoir, and needle` valves connected to the outi letsof the manifold for controlling theexhausting and filling operations. x

12. Apparatus for exhausting and filling a discharge device provided with an exhaust tube comprising a manifold having a plurality of outlets adapted to be connected to sources of vacuum andthe different filling materials, means for connecting the exhaust tube of the device to said manifold, a reservoir connected to one ,of` said outlets, a second reservoir connected to` a second outlet and to said iirstreservoir adapted to hold a vaporizable material, means of connecting the second reservoir to a source of vacuum to permit the vaporizable material to be drawn in it through the manifold, heating means for said reservoirto distill the vaporizable material into the first reservoir, and needle valves connected to the outlets of the manifold vfor controlling the exhausting and lling operations.

13. Apparatus for exhausting and lling a discharge device provided with an exhaust tube comprising` a manifold having a plurality of outlets adapted to be connected to sources of vacuum and the different filling materials, means for connecting the exhaust tube of the device to said manifold, a reservoir connected to one of said outlets, a second reservoir connected to a second outlet and to said first reservoir adapted to hold 4a vaporizable material, means of connecting the secondreservoir to a source of vacuum to permit the vaporizable material to be drawn in it through themanifold, heating means for said reservoir to distill the vaporizable material into the rst reservoir, means connected to said first reservoir for varying the pressure therein4 and "the tendency of said vaporizable material to 

